1. Field of the Invention
The present invention relates to a direct methanol fuel cell system capable of driving electronic appliances hitherto using a battery as driving power source such as small portable appliances.
2. Description of the Related Art
Recently, fuel cells have high expectations as a power source for use in portable electronic appliances supporting the age of information technology, or as measures against air pollution and global warming.
Of the various fuel cells, the direct methanol fuel cell (DMFC) for generating power by taking out protons directly from methanol has outstanding benefits, such as no need of a reformer, and small fuel amount, and its application in portable electronic appliances is being developed. It is thus expected to be applied in many fields.
As disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-93551, a container for holding a liquid fuel of a direct methanol fuel cell is detachable, or is capable of being replenished with liquid fuel, and driving for a long period is realized while reducing the size of the fuel cell.
This type of direct methanol fuel cell is required to control the concentration of the methanol aqueous solution supplied as fuel, but the optimum concentration varies according to the load, which fluctuates, and the amount of the replenished methanol. The correct-supply amount in relation to an external load is not known unless actually operated for a long time, thus a practical direct methanol fuel cell capable of generating power stably for a long period has not been developed yet.